As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to users is information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems.
External AC-DC adapters or power supplies are commonly employed to convert alternating current (AC) wall current to direct current (DC) for powering DC-powered systems, including DC-powered information handling systems such as notebook computers. DC-powered information handling systems are typically configured to operate in one or more non-operational host power states in which the host CPU is non-operational (e.g., sleeping, “soft off” or “mechanical off” states), such as Advanced Configuration and Power Interface (ACPI) G1 sleeping states S1, S2, S3, S4; G2 “soft off” state S5, and G3 “mechanical off” state. Regulatory bodies around the world are creating ever-lower specifications for maximum allowable non-operational power consumption in an effort to reduce or eliminate so called “Vampire” power. New types of non-operational host power states such as Microsoft Windows connected standby (CS) and always on always connected (AOAC) states noticeably increase the minimum power of a DC-powered system during the non-operational host power state, which increases the risk of exceeding regulatory limits for sleep or “Off” state power.
As long as the AC mains switcher of a conventional AC-DC adapter is operating during a non-operational host power state of a connected DC-powered device, a floor is established for AC power consumption that can exceed current or future established regulatory limits. To address this problem, an AC-DC adapter configuration has been previously implemented that employs a controller within the DC adapter circuitry to turn off the AC mains switcher of the AC adapter when no power supplier identifier (PSID) signals are detected by the adapter controller as being received from a connected operating DC-powered system (i.e., DC-powered system is not connected), and that allows the AC-DC adapter output voltage to bleed down during such times to a voltage level that is below established regulation limits. Other conventional AC-DC adapter configurations have been implemented that utilize an adapter controller within the AC-DC adapter to enable a low power or zero power adapter mode during detected no load or system sleep states of an attached DC-powered system. Such conventional AC-DC adapters require some user interaction with the adapter (typically requiring the user to push a button on the adapter) to recover the adapter to a normal power supplying operating mode. Anytime such a conventional AC-DC adapter is on, the adapter DC output stays in regulation limits with the primary side switcher circuitry on and running.
Some current three-wire AC-DC adapters implement a low power mode when no system is connected to the AC-DC adapter in order to get no-load AC-DC adapter power consumption to below 100 milliwatts. In particular, if the system load power of a coupled DC-powered system is below a very low power level and the AC-DC adapter senses an open circuit on the third wire (e.g., PSID pin) then the AC-DC adapter enters this low power mode. If the PSID pin gets terminated or if the load suddenly increases then the AC-DC adapter will go back into normal operation. In the low power mode the AC-DC adapter turns off the AC mains switcher and allows the output voltage to droop. The controller for the switching regulator which includes the detection capabilities mentioned above resides on the secondary side of the AC-DC adapter and will continue to operate from the energy stored in the output filter capacitors. Once the DC output voltage of the AC-DC adapter reaches a lower limit then the secondary controller of the AC-DC adapter will turn on the AC mains switcher and re-charge the output capacitors to the nominal operating voltage of the AC-DC adapter. The cycle then repeats as long as the system load power remains below a very low power level.